Replace binary Analysis format with a text-based one.

Reads/writes are a little faster with the text format,
and it's far more useful. E.g., it allows external manipulation
and inspection of the analysis.

We don't gzip the output. It does greatly shrink the files,
however it makes reads and writes 1.5x-2x slower, and we're
optimizing for speed over compactness.

[This is a squash of all the commits in #985.]